V Twin

I'm afraid I again suggest you ignore Mike L's minimum weight minimum diameter topmast. I was lost on the logic that it holds less water. It will certainly hold less air/buoyangy which is what you need initially.

Oldbarn ... more than half the problem is recovery FROM inversion.  Most boats will get there on occasion.  If you try and support /raise say 4 liters of water rather than 1.5-2 liters within a 6m or 7m mast you will find out what a significant difference it makes.  There is a LOT of leverage against you especialy when all the additonal rigging associated with a 2 or 3 sail rig.  The Vortex mast is also a bit of a clunker, and you will capsize less ofted with a low drag lightweight mast as well but that is not the main point being made.  You will not completely STOP a mast  flooding unless completely sealed when the top is 6 or 7 metres down either so it is better / safer or assume flooding as a reality if inverted for very long and have a related answer to the problem.   Sure you wan to avoid inversion in the first place but inversion is NOT the real problem here ... it is recovery from inversion.  A winged boat will 'trip' to inverted more readily if the tramps catch wind and wave (hence all the netting and string around !) than say your wingless Alto if not caught reasonably quickly in a breeze - so you really have got to be able to right from inverted without too much drama from a potential 'mast flooded' starting point.    If club sailors cannot do it with relative ease you have a whole host of problems to face .... and questions to pose.

Mike L.   

I can't see that getting from inverted 180degrees to say 110degrees is much about the volume of water in the mast. It's about the stability of the inverted hull and the amount of leverage you can assert with your weight. Only when the mast starts coming out of the water does its water content matter, although buoyancy will start to help. In my experience of inverting RS400's it is worst when you cannot get your weight on the gunwhale and lean back, because there is too much chop. The key to leverage when the boat is on its side is often having little enough buoyancy that the plate is no more than about a foot above water, and a hull shape that means a weight on the bit of plate near the hull is the right side of the centre of buoyancy at that time.
The effect of waves driving the hull over the rig is a nuisance on the 400 where I sail. That can be a real fight to prevent inversion.
I can only suggest somehow losing some hull volume when it's on its side, perhaps dividing up the hull into chambers some of which flood. Other classes have done this with vented side tanks etc.
Like most boats, I think the 400 has too much tank volume. Look at a Merlin to see all you really need!
I agree with the concept of somewhere between 4 and 10 capsizes a year being acceptable, we'd have been close to the 4 in the RS400 last year if we had packed up in October, I blame our spate of winter capsizes on fumbling with gloves on. Alas I managed a good few capsizes crewing an 800, but they respond quite well to 2 engineers stood on the rack when inverted.

A problem with boats that have low tank volume (N12 AC and my old Lark) is that when they do come up they are just about swamped they are super unstable until the water gets going out.

Originally posted by oldarn Regarding inversion, it is best to minimise the likelihoohy of this happening,

Only if you like being an almost invisible head in the water watching a boat on its side being blown downwind faster than you can swim...

Personally, if there's no-one on board, I want my boat to invert whilst it's still within swimming distance. A large mast with small holes at the top isn't a bad solution to this since it will float for a while, but such masts aren't great when you don't chuck it in these days.

Pop a keel on it & launch from the harbour - inversion problem 99% over & once the rig is sorted you will have a ball!